Astronomija kratka povijest problematike

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Astronomijakratka povijest problematike
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Podrucje interesa

• Planeti
• Suncev sustav
• Zvijezde
• Meduzvjezdani prostor
• Galaksije
• Aktivne galakticke jezgre (AGN)
• Kvazari (eng. quasar - quasi-stellar radio
  source)
• Klasteri galaksija
• Pulsari (brzorotirajuce neutronske zvijezde)
• Svemir

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Suncev sustav

• Fizika Sunca
• Solarni vjetar
• Planeti
• Njihovi sateliti
• Asteroidi
• NEOs (eng. Near eart objects)
• Pojasi
• Interplanetarna prašina

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Zvijezde

• promjenjive zvijezde
• dvojne zvijezde
• patuljci, divovi
• Supernove
• kompaktni objekti (crne rupe, bijeli patuljci,
  neutronske zvijezde)

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Meduzvjezdani prostor

• Nastanak zvijezda
• Astro-kemija
• Struktura i razvoj zvijezda
• Nuklearna astrofizika

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Galaksije

• Nastanak i formiranje
• Struktura
• Naseljenost
• Dinamika

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AGN (Aktivne galakticke jezgre) Kvazari

• nastanak
• klasifikacija
• gorivo
• evolucija
• gustoca

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Klasteri

• Nastanak i razvoj
• Struktura
• Tamna tvar
• Gravitacijske lece

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Svemir

• Starost i velicina
• Nastanak i razvoj
• Tamna materija , stringovi, egzoticne cestice
• Topologija (oblik)

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Znanstveni elementi u astronomiji

• Promatranje
• Zemaljsko (opticko, infracrveno, radio)
• Vanplanetarno (sateliti i satelitske platforme
  UV, x-ray)
• Racunanje
• Analiza podataka
• Kompleksni problemi
• Numericke simulacije

• Analiza
• objektivnost
• asimiliranje formi i podataka
• linearno nelinearno razmišljanje
• Pisanje
• publikacija
• prijedloga
• prezentacija

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Zapošljavanje (danas)
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Što astronomi ne rade

• Pišu horoskope
• Imaju vezu s vanzemaljskim civilizacijama
• Memoriraju konstelacije
• Cijelo vrijeme gledaju kroz teleskop

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Radioastronomija

• Kozmicko zracenje 3K

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Elektromagnetski valovi
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Ehn cln
Kraco valovi Veca energija Viša frekvencija
Duži valovi Niža energija Niža frekvencija
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Elektromagnetski spektar
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Elektromagnetski prozor kroz atmosferu!
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Izvori elektromagnetskog zracenja

• Termalni
• Zracenje crnog tijela
• Kontinuirana emisija ioniziranog plina (plazma)
• Emisija spektralnog zracenja atoma i molekula

• Netermalni
• Sinkrotronsko zracenje
• MASERS

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Plankov zakon
u(?,T) 4pI(?,T) / c
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Zracenje crnog tijela - Sjaj
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Sjaj elektromagnetskog zracenja razlicitih valnih
dužina za crno tijelo na razlicitim temperaturama
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MASER
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Sinkrotronsko zracenje

• Polarizacojska svojstva EM zracenja daju
  informacije o geometriji magnetskog polja

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Sinkrotronsko zracenje
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Zakon obrnutog kvadrata !
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Zabluda
Radio program koji se ne sluša!
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Radio Teleskopi

• Dvije izvedbe

Very Large Array, NM
Polje radio antena
Radio antena
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The Very Large Array (VLA)

• 1980 godine
• Dvadest sedam 25-metarskih rekonfigurabilnihantena
  Socorro, NM
• Više publikacija od bilo kojeg teleskopa na
  svijetu

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Very Long Baseline Array (VLBA)

• 1993 godine
• Operirane oz Socorro-a
• Deset 25-m antennas diljem SAD, Kanade, P.R.
• Najviša rezolucija

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Pocecieksperiment Janskog

• Promatra nemodulirani doprinos RF
• (static)
• Postepeno s mijenja intenzitet s
• periodom od gotovo 24h
• Sunce izvor?
• maksimum 4 minute rani svaki dan
• Izvor izvan Sunceva sustava
• Izvor u Mljecnoj stazi!
• 1933 objavljuje rezultate

Karl G. Jansky (1905-1950)
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Reberov tip radioteleskopa

• Despite the implications of Janskys work, both
  on the design of radio receivers, as well as for
  radio astronomy, no one paid much attention at
  first.
• Then, in 1937, Grote Reber, another radio
  engineer, picked up on Janskys discoveries and
  built the prototype for the modern radio
  telescope in his back yard in Wheaton, Illinois.
• He started out looking for radiation at shorter
  wavelengths, thinking these wavelengths would be
  stronger and easier to detect. He didnt have
  much luck, however, and ended up modifying his
  antenna to detect radiation at a wavelength of
  1.87 meters (about the height of a human), where
  he found strong emissions along the plane of the
  Milky Way.

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Reconfigurable Arrays Zoom Lens Effect
VLA

• Više detektora bolja rezolucija

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Radio Telescopes Sensitivity

• Sensitivity (how faint of a thing you can see)
  depends on how much of the area of the
  telescope/array is actually collecting data

• VLA B-array Total telescope collecting area is
  only 0.02 of land area
• More spread-out arrays can only image very
  bright, compact sources

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Parabolic Dish
Green Bank Telescope, WV
Sub-reflector

• Aluminum reflecting surface
• Focuses incoming waves to prime focus or
  sub-reflector

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Sub-reflector
Sub-reflector

• Re-directs incoming waves to Feed Pedestal
• Can be rotated to redirect radiation to a number
  of different receivers

Feed Pedestal
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Feed Pedestal
1.5GHz 20cm 2.3GHz 13cm 4.8GHz
6cm 8.4GHz 4cm 14GHz 2cm 23GHz
1.3cm 43GHz 7mm 86GHz 3mm
327MHz 90cm 610MHz 50cm
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Antenna Feed and Receivers
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Benefits of Observing in the Radio

• Track physical processes with no signature at
  other wavelengths
• Radio waves can travel through dusty regions
• Can provide information on magnetic field
  strength and orientation
• Can provide information on line-of-sight
  velocities
• Daytime observing (for cm-scale wavelengths
  anyway)

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Primary Astrophysical Processes Emitting Radio
Radiation
When charged particles change direction, they
emit radiation

• Synchrotron Radiation
• Charged particles moving along magnetic field
  lines
• Thermal emission
• Cool bodies
• Charged particles in a plasma moving around
• Spectral Line emission
• Discrete transitions in atoms and molecules

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Thermal Emission

• Emission from warm bodies
• Blackbody radiation
• Bodies with temperatures of 3-30 K emit in the
  mm submm bands
• Emission from accelerating charged particles
• Bremsstrahlung or free-free emission from
  ionized plasmas

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Nobelova nagrada za otkrice kozmickog mikrovalnog
pozadinskog zracenja
Robert Woodrow Wilson
Arno Allan Penzias
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The Nobel Prize in Physics 1993

• for the discovery of a new type of pulsar, a
  discovery that has opened up new possibilities
  for the study of gravitation"

Russell A. Hulse
Joseph H. Taylor Jr
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Spectral Line emission hyperfine transition of
neutral Hydrogen
Emits photon with a wavelength of 21 cm
(frequency of 1.42 GHz)
Transition probability3x10-15 s-1 once in 11
Myr
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Spectral Line emission molecular rotational and
vibrational modes

• Commonly observed molecules in space
• Carbon Monoxide (CO)
• Water (H2O), OH, HCN, HCO, CS
• Ammonia (NH3), Formaldehyde (H2CO)
• Less common molecules
• Sugar, Alcohol, Antifreeze (Ethylene Glycol),

malondialdyde
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Spectral Line Doppler effect

• Spectral lines have fixed and very well
  determined frequencies
• The frequency of a source will changed when it
  moves towards or away from you

• Comparing observed frequency to known frequency
  tells you the velocity of the source towards or
  away from you

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Special example of Spectral Line
observationDoppler Radar Imaging
bounce off object
Transmit radio wave with well defined frequency
..observe same frequency
NASAs Goldstone Solar System Radar
Very Large Array
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Brief Tour of the Radio Universe

• Solar System
• Sun, Planets, Asteroids
• Galactic objects
• Dark clouds, proto-stellar disks, supernova
  remnants,
• Galaxies
• Magnetic fields, neutral hydrogen
• Radio Jets
• The Universe

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Wilkinson Microwave Anisotropy Probe (WMAP)
map.gsfc.nasa.gov
Background3 K blackbody radiation
Shepherding in the era of Precision Cosmology
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image of the cosmic microwave background
radiation anisotropy. It has the most precise
thermal emission spectrum known and corresponds
to a temperature of 2.725 kelvin (K) with an
emission peak at 160.2 GHz
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Radio pregled Mljecne staze
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(a) radio (b) infrared, (c) visible (d)
X-ray Each illustration shows the Milky Way
stretching horizontally across the picture.
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Pulsar

• Pulsars are highly magnetized, rotating neutron
  stars that emit a beam of electromagnetic
  radiation. The observed periods of their pulses
  range from 1.4 milliseconds to 8.5 seconds. The
  radiation can only be observed when the beam of
  emission is pointing towards the Earth.
• This is called the lighthouse effect and gives
  rise to the pulsed nature that gives pulsars
  their name. Because neutron stars are very dense
  objects, the rotation period and thus the
  interval between observed pulses are very
  regular. For some pulsars, the regularity of
  pulsation is as precise as an atomic clock.
• Pulsars are known to have planets orbiting them,
  as in the case of PSR B125712. Werner Becker of
  the Max-Planck-Institut für extraterrestrische
  Physik said in 2006, "The theory of how pulsars
  emit their radiation is still in its infancy,
  even after nearly forty years of work.

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Kvazar

• A Quasi-stellar radio source (Quasar) is a
  powerfully energetic and distant galaxy with an
  active galactic nucleus. Quasars were first
  identified as being high redshift sources of
  electromagnetic energy, including radio waves and
  visible light, that were point-like, similar to
  stars, rather than extended sources similar to
  galaxies.
• While there was initially some controversy over
  the nature of these objects as recently as the
  1980s, there was no clear consensus as to their
  nature there is now a scientific consensus that
  a quasar is a compact region 10-10,000
  Schwarzschild radii across surrounding the
  central supermassive black hole of a galaxy,
  powered by its accretion disc.

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Maser

• edit Historical background
• In 1965 an unexpected discovery was made by
  Weaver et al.3 - emission lines in space of
  unknown origin at a frequency of 1665 MHz. At
  this time many people still thought that
  molecules could not exist in space, so the
  emission was at first put down to an interstellar
  species named Mysterium, but the emission was
  soon identified as line emission from OH
  molecules in compact sources within molecular
  clouds4. More discoveries followed, with H2O
  emission in 19695, CH3OH emission in 19706
  and SiO emission in 19747, all coming from
  within molecular clouds. These were termed
  "masers", as from their narrow line-widths and
  high effective temperatures it became clear that
  these sources were amplifying microwave
  radiation.
• Masers were then discovered around highly evolved
  Late type stars First was OH emission in
  19688, then H2O emission in 19699 and SiO
  emission in 197410. Masers were also discovered
  in external galaxies in 197311, and in our own
  solar system in comet halos.
• Another unexpected discovery was made in 1982
  with the discovery of emission from an
  extra-galactic source with an unrivalled
  luminosity about 106 times larger than any
  previous source12. This was termed a megamaser
  because of its great luminosity, and many more
  megamasers have since been discovered.
• Evidence for an anti-pumped (dasar) sub-thermal
  population in the 4830 MHz transition of
  formaldehyde (H2CO) was observed in 1969 by
  Palmer et al.

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